Clashing beam particle accelerator



April 11, 1961 R. J. BURLEIGH CLASHING BEAM PARTICLE ACCELERATOR 5 Sheets-Sheet 1 Filed July 15, 1959 ommv T HNF NER IGRUI Awe M S 7 3 w f \\III/ 4 w ,1 0

w w o INVENTOR. RICHARD J. BURLEIGH 72 PULSED POWER SUPPLY ATTORNEY.

April 11, 1961 R. J. BURLEIGH 2,979,635 I CLASHING BEAM PARTICLE ACCELERATOR Filed July 15, 1959 3 heets-Sheet 2 FIELD SENSING n ELEMENT FREQUENCY 5O CONTROL E '59 OSCILLATOR I8 38/ OSCILLATOR OSCILLATOR POWER POWER SUPPLY SUPPLY J 6/ 3 29' 36 OSCILLATOR j 1/ 32 ai 2a 33' 'J 59 36 28 FREQUENCY J CONTROL 26 FIELD SENSING INVENTOR. ELEMENT RICHARD J, BURLEIGH April 11, 1961 R. J. BURLEIGH CLASHING BEAM PARTICLE ACCELERATOR 3 Sheets-Sheet 3 Filed July 15, 1959 INVENTOR. RICHARD J. BURLEIGH ATTORNEY.

ingly increased.

2,979,635 CLASHING BEAM PARTICLE ACCELERATOR Richard .7. Burleigh, Berkeley, 'Calif., assignor to the United States of America as represented by the United States Atomic Energy Commission Filed July 15, 1959, Ser. No. 827,499

14 Claims. (Cl. 315-518) This invention relates to apparatus for accelerating beams of chargedparticles and, more particularly, to an accelerator producing two oppositely directed particle beams and having provisionfor colliding the two beams to produce high energy nuclear interactions.

Cyclotrons, synchrotrons, and other-existing forms of high energy charged particle accelerator have heretofore been designed to accelerate a single beam composed of particles having a substantially uniform circulatory direction, which beam is caused to impinge upon a stationary target for the purpose of inducing various types of inter action between the high energy particles and the target material. In the design of such machines, interest has centered on increasing final beam energysince the range of phenomena which can be studied is thereby correspond- Several, difficult obstacles are encountered, however, in attempting to reach beam energies higher than that obtainable with existing equipment, lie,

in obtaining energies exceeding a'few billion electron volts.

, Using conventional design concepts,- thecost of multi-' bev. accelerators becomes excessive and the physical size of the apparatus must also be very large. In addi-' tion,-operational problems with respect to obtainingsufiicient beam intensity and beam stability become severe.

The'net result of these-considerations is to make theattain'rnent, of extreme'high energies a difiicult and costly undertaking and a clear need exists for a fundamental- 'new approach to thedesign of suchaccele'rators.

I Inaddition to the stated design and cost problems'associatedwiththe use of conventional techniques to achieve high energy, a further and extremely significant limitation exists on theeifectiveness ofth conventional accelerator iior-nhighenergy,,studies.- The eifective energy of a moving particle, insofar as interactionwith a stationary particle is concerned, is dependent upon 't he'ratio of" the V mass of the moving particleto that of the'sta tionary pairticle, the efiect beinga direct consequence of'the con-f servation of energy and momentum} Assuming, for pur. I poses of'discussion, that"thefjinteraotions are perfectly elastic; a .scomplete,transfer-jot energy from: moving particle; to stationary particle cantake place onlyfif" the masses of thetwopa'rticles areequal; If,,th'e masses or V .the panticles are unequal, the energy transfer. must beincomplete and moreover'dhediscrepancy' in'-j'energy t ans .feriricreases exponentially with'respect tdthefmasgsiirhbal ance. Thus doublinglthe energy' of'a'fmoving particle does not double its e fictivelienergy with respect to station aryj particle provided ia mass; imb'alance exist 2,979,635 Patented Apr. 11, 1961 have a greater mass than the stationary target proton. Moreover since the mass of the bombarding proton increases exponentially with energy, the discrepancy between absolute particle energy and available particle energy becomes increasingly severe as accelerators are made larger. The specified effect therefore seriously reduces the experimental usefulness of verylarge accelera tors which are constructed in accordance with conventional design concepts.

To illustrate the severity of this limitation, it may be shown that a proton accelerated to 6 bev. has an effece tive interaction energy of only 1.968 bev. with respect to a stationary target proton, the controlling relationship being:

1) 2)"-i- 1 a where:

W=total energy, including all rest masses, available in the center of mass system,

m =rest mass of the stationary target particle, m =rest mass of the accelerated particle,

E =total energy in the laboratory system of the ac celerated particle including the rest mass thereof. From the above relationship the effective energy of a 500 bev. proton striking a stationary proton may be shown to be only 28.809 bev. and thus the gains from going to extraordinarily high energies, assuming such to be tech nically feasible, are proportionately slight. increasing the output energy of conventional accelerators thus gives a diminishing return and an energy level presumably exists where the slight increase in effective energy to be gained fails to justify the extreme expense of achieving it.

As a new and economical approach to accelerator de-' sign and particularly as a means of overcoming the foregoing eifective energy limitation, it has been suggested that the desiredparticle interactions be produced bycol liding two oppositely directed similar high energy particle beams. Under these conditions, the colliding particles are each traveling at the same velocity and their masses are therefore equated; Owing to the lack of any mass imbalance, the energy available'for interaction is essen-' tially. the sum of the energies of the-two particles and the energy limitation'hereinbefore discussed is overcome.

By eliminating the discrepancy between real energy and available energy, the resultant particle interactions-are equivalent to those 'producedby a conventional accelera ,tor having a beam energy far exceeding the sum of the energies of the colliding'beams. Usingthe relationship hereinbefore given; the interaction energy available through the collision of two 6:15 bev.- proton beamswill a be found to'equal that available in the collision of allOO bev. protonwith a stationary protons Thus while the construction of-a conventional accelera V tor to produce a l0O bev. proton beam willfpose formidable problems, effectively the same resultscan'be achieved highly advantageousftechnique for achieving extremely a energy fjparticle interactions. 7 -f Cons idering n specific nieanswith whichithe collision of particlebeamsw' can be effected, ithasbe'en proposedj that two circular by colliding two beams each of which'hasi fan energy ofonly:6.15 bev. whichlatter energy has been achieved with 1 exis ing equipment of conventional design.

' I The use of colliding o'r clashing beams isqthereforea accelerators of'the protonsynchrotron cl the 'twobeams' of which'frotate in opposite enses;

'two" accelerators were to be disposedin a tangentiahre )7 in? la'tionship, ilewith a: singletcommon point on 'theorbits is i gof each,".suchlhattthejbeams may jf'belclashedg at the commonrpoint'ginthe-orbits to,:produce -j:the1desired'tre actions:Q-Wl'aile the accelerators? might conceivabl vspaced;apart'and-theqbean f each extractedt r co be. Y.

3 at some intermediate point, the difiiculties associated with extracting a sufiicient proportion of the beam from accelerators of this type would make this configuration a much less effective one. i As an alternate method, it has been proposed that a single accelerator be used together with a beam storage means disposed adjacent the accelerator. In this system a beam is accelerated in a first rotational sense and transferred to the storagemcans- Subsequently a second beam is accelerated with a reverse rotational sense and collided with the first, or stored, beam. Inasmuch as the storage means is an annular magnet structure somewhat similar to that of the accelerator, this method of colliding beams is only slightly less costly, and physically about as large, as the two accelerator method. In addition, the duty cycle must be less than one half that of the two accelerator method since a collision can at best be effected only on alternate pulses of the accelerator magnet.

Thus while the clashing beam concept presents an excellent method for achieving high energy reactions, the apparatus as heretofore envisioned requires large quantities of costly equipment and space.

The present invention provides a more economical, compact, and efiicient clashing beam accelerator with which extreme high energy particle interactions can be readily accomplished. Specifically the invention utilizes a single annular magnet structure within which two concentric contra-rotating. ion beams'lare accelerated, one beam orbit being of slightly less diameter than the other. At one section of the magnet deflector means are provided which deflect the inner beam to a greater orbital radius while simultaneously deflecting the outer beam to'a lesser radius thus causing the two beams to collide head on. A further property of the deflecting means is to return those particles which do not undergo collision to the original orbits so that the particles re-circulate within the accelerator with the possibility of producing'interactions on subsequent turns. t

By means of the foregoing unique structure, particle interactions at energies far greater than those heretofore artificially produced can be effected with an accelerator mechanism not appreciably more costly or larger than conventional accelerators of comparatively low efiective energy.

It is accordingly an object of this invention to provide an improved means for inducing high'energy interactions between particles.

It is anotherobject of this invention to. provide' a charged particle accelerator-capable of achieving nuclear interactions at far higher efiective energies than have heretofore been possible.

It is an object of this invention to provide a clashing beam particle accelerator of comparatively economical cost and small size with respect to earlier designs.

It is still a further object of the'present invention to provide a compact efficient accelerator for colliding oppositely directed high energycharged particle beams.

It is an object of the invention to" provide aclashing beam charged particle accelerator requiring only a single annular magnet structure.

' It is an additional object of this invention to provide a charged particle accelerator for ,colliding oppositely directed particle beams to produce interactions therebetween and in which the region of beamcollisioh is relatively free from obstruction whereby the interactions may be more conveniently and completely studied.

the following specification together with the accompanying drawings, of which:

Figure 1 is a plan view offan accelerator and appurtenances with certain conventional components thereof being shown in block form;

Figure 2 is an enlarged view of the portion of Figure 1 encircled by the dashed line 2 thereon and showing a typical segment of the principal magnet of the acceleratr;

Figure 3 is an enlarged cross section view taken along 3-3 of Figure 1 and showing internal details of the principal magnet;

Figure 4 is an enlarged plan view of the portion of Figure 1 encircled by dashed line 4 thereon and showing the beam accelerating region of the accelerator together with components, shown in block form, for providing radio-frequency excitation thereto;

Figure 5 is an enlarged plan view of the portion of Figure 1 encircled by dashed line 5 thereon and showing the beam clashing section of the accelerator;

Figure 6 is a section viewtaken along line 6--6 of Figure 5 further illustrating the beam clashing region of the accelerator; and

Figure 7 is a cross section view taken along line 7-7 of Figure 6.

Referring now to the drawing and more particularly to Figure l, the general configuration of the accelerator will be described, the detailed structure of the various component parts thereof being hereinafter described with reference to later figures.

The accelerator comprises an annular electro-magnet structure 11 segmented into four separate quadrant sectors 12, 13, 14, and 16 the quadrants being spaced apart a small distance to provide straight sections 1'7, 18, 19, and 21 on the particle orbits which sections are utilized for such operations as beam injection, acceleration, and beam collision. The described construction of a large accelerator magnet in spaced quadrants is a conventional practice well understood within the art, and it should be observed that the resultant distortion of the beam orbits from exact circularity, occasioned by the presenceof the straight sections 17, 18, 19, and 21, does not deleteriously afiect'the beam dynamics and the presence of such sections may be disregarded insofar as the analysis of interactions betweencharged particles and the field of the magnet is concerned.

For convenience in construction, to facilitate adjustment, and to expedite the replacement of defective or damagedromponents, each of the magnet quadrants 12, 13, 14, and 16 is in turn formed of four discrete sections 22, each of which sections is providedwith separate windings as will hereinafter be described. 1 It should be. understood that the construction of the magnet quadrants in sections 22 is a convenience rather than a necessity and that various numbers of sections per quadrant can be used if desired.

Referring now to Figures 2 and 3, the magnet sections 22 are in turn each formed of four sub-sections 24, alternate ones of the sub-sections being designated by the numeral 24. As shownin Figure 3 in particular, each sub-section 24 1and 24 comprises allower' portion 26 of U-shaped cross;.section and a similar but inverted upper portion 27, the upwardly extending-arms 28 of the lower portion'beiug spaced a small distance. from the downwardly extending arms 29 pf the upper portion. Two

It is still'a further object of this inventionto provide a particle accelerator having provisionfor establishing two. concentric contra-rotating particle beams and having means for deflecting the beams to achievea collision therebetween and for returning the beams to the original orbitsthereof for recirculationwithin the-accelerator;

The invention, together withfurtherbbjects and advantages thereof, will best be understood by reference-to magnetggaps al-uand 32 are thusformed; gap 32 being radially innermostwith'respect to the overall curvature of the magnet structure. To provide a strong focussing action on particle. beams circulating within themagnet gaps 31 and 32, the pole tips 33 and 34 of magnet arms 28. and 29 respectively are curvedso thatxthe gaps 31 and 32 are of exponentially increasing. height outward froma midpoint between the two gaps. Methods for j ,calculating" the precise curvature of pole tips .33 and '34 to achieve; the :desired stron'g ior alternating gradient,

focussi'ng action in .aparticular system are well under.-

stood and may be studied by reference to US. Patent No. 2,736,799 entitled Focussing System for Ions and Electrons and issued to Nicholas Christofilos, February 28, 1956, It will be noted that to achieve this form of beam focussing, the curvature of the pole faces 33 and 34 on the alternate sub-sections 24' must be reversed from that of the intervening sub-sections 24, the gaps between the pole faces of the alternate sub-section 24 being of decreasing height outward from the midpoint of the magnet structures. It will be understood that other forms of beam focussing may be employed with the accelerator if desired and in utilizing certain of the various known forms of focussing, the curvature of all pole tips may be the same.

Each of the magnet sections 22 utilizes'four windings 36, one encircling a first set of arms 28 of each of the four sub-sections 24, one encircling the opposite set of arms 28, and the remaining two being correspondingly placed on the upper magnet portions 27. As shown in Figure 1, all the magnet windings 36 of each of the four magnet quadrants arev connected in series relationship and are excited by a suitable source 37 of pulsed direct current.

With respect to the design of the magnet 11, it will be found advantageous if the two particle beams have exactly the same energy at the time of collision. Therefore, since the radius of the inner orbit is less than that of the outer orbit, the magnetic field across the inner orbit must be proportionately stronger than that across the outer orbit if beams of equal energy are to be containe'd. Thisis accomplished by proportioning the par-,

'ticular pole'pieces '33 and 34 which are associated with the inner orbit to be of less lateral Width than the poles at the outer orbit thereby concentrating thevflux across the inner gap 32. Alternately an iron shunt across the outer gap 31 may be employed to reduce the relative flux thereacross. h Referring now to Figures 1 and 3, two annular vacuum envelopes are disposed within the magnet structure, a

first such envelope 38 'being centered within the outermost magnet gap 31 and the second envelope 39 being I within the inner gap 32 and therefore being of a slightly lesser-diameter. Each of the vacuum envelopes 38 and 39 conform to the magnet structure in having four spaced apart quadrantse'ctions joined by straight sections and each envelope .is of circular cross-section except at speouter vacuum envelope 38 at an acuteangle. Inasmuch as the bulk of the magnet structure will generally prevent the axis of accelerator 42 from being aligned tangentially magnet 11 during the pulsing thereofwill circulatearound the axes of two vacuum envelopes 39 and 38 provided the field of the magnet at the time of injection is'prop- .zerly matched to the particle energy, mass, charge and cialized points as will hereinafter be described, .It will,

be apparent thata single large vacuum tank encompassing both particle orbits might be utilized if desired;

the use of two separate envelopes as described above being advantageous from the standpoint ofreducin'g the volume which must be pumped to high vacuum. .Con-

" a sidering now means for evacuating the envelopes 38 and 39, two banks of diffusionpumps 41 are situated in one of the magnet" straight'secti0ns21 one half of thepurnps being connected with the outer envelope 38 and the If space limitations permit the arrangement, it may be 7 others being connectedwith the inner envelope 39.

found preferable to" distribute the pumps around the ,twoenvelopes as theipumpingspeedfwill be thereby e'nhanced.

Considering .nowiprovision for the injection of charged particles into the two beamorbits within the two'vacuum envelopes ftfi and,39, it is a characteristic of accelerators of the proton synchrotron class. that particles1mustbe in "'--"':,jected into-,the {beam orbit with ari a'pprec -ziable initial. energy and thus a smaller accelerator must be utilized as;

a pre-ac'celerator, :As'shown in Figure 'l,:a:first linear s accelerator 42, which may. be of-tjhe type disclosed in I t;U;S.,Ratent;2,545,595 issued to LuisHW. "Alvarez March "20, 195 1, and" entitled Linear Accelerator, jand which is provided with anionsource 43,:is positionedfadjacent the agnet straight section 1'7 4 and I outside the area enclosed V I ythemagnet;The linear' accelerator 421s positioned to rem'it high energy particles along an axis" transectingthe' jquate 's'pace for a saturable. -reactor which .inafter:.describ'ed, the openings 56', and }thu s th 'ibe am," V orbit throughfthe resonator, is;off-centergwith.:respecu'to 1 shell 54 the major-'voluineof-the shellbeing-towardsthe:' insidefof the fmagnetj;'11. A cylindrical re-entrant sec- 1- non- 57, having slightly les nlen'g th and considerablyless- ,diameternthanithe shell 5,,4il s disposedwithin thelresona;

tor .COaxiallvWith respect'to thefbpe ni ngs '56.: f The retentrant sectionfi'i is disposed withigoneiend,in lcontacti 7 it withone enawau 'ofjthe; shell softhauhe opposite end of the s'ec'tion is spaceda small distance from the opening 56..i i1theshell-"formingan accel il'ating'gap*58. I

beunderstood that boththeshell'54fa1 r$entrantse6i 1 with respect to the beam orbit within the envelope 38, an arcuate electrostatic beam deflector 44 is provided to bend the beam from linear accelerator 42 into colinearity with the beam orbit of the envelope, the deflector being hermetically sealedvand evacuated by communication with the vacuum regions of the envelope and the accelerator 42. t v To inject charged particles into the inner beam orbit, i.e., into vacuum envelope 39, a second similar ion source 46 and linear accelerator 47 are disposed adjacent the magnet straight section 17 within the area encircled by the magnet structure. Such second linear accelerator 47 is positioned to emit a beam towards the vacuum envelope 39 at an acute'angle thereto and opposite" to the direction of the'beam from the first linear accelerator 42, a second vacuum tight arcuate beamj deflector 48 being provided to bend the beam into colinearity with the axis of the envelope. Thus the beams which are injected into the two orbits of the magnet 11 are, oppositely directed, the beam in theouter envelope 38 being of a counter-clockwise rotational sense in this instance and r able reversing field beam steering magnet being utilized.

to deflect particles alternately into the outer orbit and into the inner orbit.

' v Particles injected into the two beam orbits within the orbit radius in accordance with the well-known relationships governing such orbits Considering now means by which the particles are further accelerated as the magnet I field increases. thereby maintaining a substantially constant orbit, a first and second accelerating system .49 and 50 respectively are disposedat the magnet; straight section 18, the first system 49 being operativeon the outer beam orbit and thesecondsystern 50 acting on the inner orbit. I v Referring now to Figure 4, the

Except insofar asitwov separate accelerating systems. are

utiIized the beam acceleratingcomponents of theinvention make use of conventional design concepts, well un-3 derst'oodwithinthe art, and accordingly certain elements of the electrical circuitryare shown in block form: Considering first the innertorbit RF sy'stem 50, to .which the outer orbit System49 is similar, are-entrant cavity -r eso nator 51 is positioned around a gap in the straightsection'of vacuum envelope '39. Theresonator' 51 comprises, a cylindrical outer "shell" 54 havinglopposed end ope ng 16 intciwh thet ds q the acu mem 1- 39 arefittedand secured soithati thejshelll is effectively an e'nla'rge'd' segment er the envelope. To provide adev region of the accel'-' erator ad acent straight se cti0 ,,18 is shown in more de-' tail, together with the -component members a'ndtassoci aremassa e tion 57 are formed of electrically conductive material and are vacuum tight. 7 Y

' To establish the necessary alternating electrical field across the accelerating gap 58, the resonator 51 is energized by a cavity tuned RF oscillator 59 which is in turn provided with a suitable power supply 61. Thus, if the resonant frequency of resonator 51 is matched to the period of revolution of particles within the accelerator orhit, the particles may be made to cross the gap 58 once each RF cycle and at a phase therewith whereby the particles receive an increment of energy from the field across the gap. It is apparent, however, that as the particles are accelerated the period of revolution decreases and accordingly the frequency of resonator 51 must be correspondingly increased tomaintain the necessary phase relationship.

As has'been previously discussed, the field of magnet 11 also increases as the particles are accelerated thus holding the particles in a substantially constant orbit. Therefore control of the accelerating system frequency can be conveniently efiected by obtaining a signal indicative of the instantaneous value of the magnetic field and utilizing such signal to control the frequency of the resonator 51. As a means for varying the frequency of the resonator 51, a saturable reactor 62 is disposed within the outer resonator shell 54. The reactor 62 comprises a cylindrical ferrite core 63 having an off-center longitudinal passage through which the re-entrant section -57 passes and having a winding 64 through which a current may be passed to vary the inductance of the reactor. Such change of inductance produces a corresponding change in the operating frequency of the oscillator resonator system anditherefore serves to match the frequency of the electric field across gap 58 with the decreasing pe-.

riod of revolution of particles within the accelerator. To control the saturable reactor 62, and thus to control the operating frequency. of the system, a suitable magnetic field sensing element 66 is positioned adjacent the magnet 11 and serves to deliver a signal indicative of the instantaneous value of the magnetic field to a reactor inductance control unit 67. The control 67 varies the energization of reactor windings 64 in accordance with the changing signal from sensing element 66, the particular level and rate of change of; such energization being dependent upon the specific parameters of a given'accelerator. A i I i To provide for the acceleration of particles in the outer orbit, a second oscillator resonator system is provided which system is similar to that described but which operates through a slightly lower frequency range owing to the slightly greater period of revolution of particles in the' outer orbit. The'duplicate system comprises a second'cylindrical re-entrant resonator 51 positioned in a gap in the straight section 18of outer vacuumenvelope 38, and forming an enlarged segment thereof As in the previous instance, resonator 51 is provided with a cylindrical re-entrant section 57' centered on the axis of 'the vacuum envelope 38 and terminated short of one end of the resonator to form an accelerating gap 58. A ferrite saturablereact'or 62' is disposed within the res- '8 comprising spaced apart deflector magnets 69 and 71 energized by a pulsed power supply 72.

Referring now to Figures 5, 6,and 7, elements of the beam clashing system at straight section 19 are shown in more detail, the deflector magnets 69 and 71 being shown disposed one at each end of the straight section and with a substantial spacing between the two magnets. The vacuum envelopes 38 and 39 are merged together substantially throughout the length of the straight section to form a single broad vacuum tank 73 having a lateral width exceeding the separation of the two beam orbits.

Considering now the structure of the deflector magnet 69 the'magnet is comprised of an upper section 74 disposed above tank 73 and provided with two pole pieces 76 and 77 which are spaced along the upper surface of the tank, pole 76 being closest to the accelerator magnet 11. Each such pole piece is encircled by a separate winding 78. Directly beneath the upper section 74 is a similar but inverted lower section 79 having upwardly facing pole pieces 81 and 82 on the opposite side of tank 73 from pole pieces 76 and 77, respectively. Encircling each of the lower pole pieces 81 and 82 is a separate winding 83.

The second deflector magnet 71 is of similar design, comprising an upper section 84 with pole pieces 86 and 87 encircled by separate windings 88 and a similar but inverted lower section 89 having upwardly facing 'pole pieces 91 and 82 energized by separate windings 93, the pole pieces 87 and 92 being nearest the magnet 11.

The relative polarities of the pole pieces, and thus the manner of electrical connection between the various pole piece windings, ofthe'deflector magnets 69 and 71, are determined by the requirement that the two particle beams be brought tocomrnon intermediate radial position at the center of straight section 19 and then diverged to return to the original orbits. The necessary polarities to accomplish this are dependent upon the charge and rotational direction of the two particle beams and the onator 51" and is providedhwith windings 64' for con- 'tr'ollably varying the inductanceEof the reactor; Anoscil- 'lator' 59, with power supply61' is"utili'zed"to energize -the resonator '51 and the resonant frequency Y of the, system isfdetermined bya magnet field sensing elernent 66' coupled to a reactor' winding'cnrrent control '67.

By means or thefdescribe'd duplicate accelerating systems; the oppositely?directed; charged particle beams withinthe two yacuurn envelopes 38 and 39 are eac h accelerated to highi'en'ergy, the increasing fieldof the mag- :net 11 serving to hold the particles in' a substantially ;constant.orbit. Whenthe desired energy level has been I reached, and with reference to Figure 1 collision of the .two'b'eams is ffedtdby a deflectorrmagnet' system sitish fss t qnria. teamers general relationship is that the first of the deflector magnet fields encountered by the oncoming beam in the outer orbit should be of like polarity to the main accelerator magnet 11 in the outer orbit, the second and the third of the deflector fields traversed by the outer beam should be of opposite polarity and the last deflector magnet field to. be traversed by the said outer beam should again have a polarity similar to that of the main accelerator magnet 11 at the outer orbit thereof. With appropriate field intensities, the effect of this sequence of fields is to first curve the outer beam inward towards the center of the accelerator and then to sequence of fields on the inner orbit beam is to first deflect the beam outward and then to straighten the beam out along the centerline of tank 73 where it is coincident with, and oppositely directed to, theouter beam thereby 'efiecting the desired particle collisions Subsequently,

the inner beam isvdeflected inward and then curved to return tothe inner beam orbit of the main accelerator magnet 11.

' Referring-now to Figure 6 in particular, a specific example of suitable deflector magnet polarities'is shown,

the beams being a'ssumed'to be positively charged particles and to be circulating counter-clockwise in the outer ,orbit and'clockwisein the inner orbit. Under these conditions, the magnetic field ofthe main accelerator magnet 11 must, in the region ofthe outer orbit, be directed 'downwardand must be directedupwardin theregion of theinner orbit. Thus in accordance, with the foregoing generalized'rule, the field between polefaces 76and S1 and thefield between pole faces 8'] and ,92

that??? att st d g e dt tuis ist qkil np.Hrahd be readily placed at any of various positions.

thefield'between pole faces 77 and 82 and that between pole faces 86 and M must be directed upward as indi cated'by lines H. It will be understood that variations in'the described magnet polarity are possible, for example all polarities including that of the main magnet 11 may be reversed and satisfactory operation effected if "each charged particle beam is injected into the accelerator with a reversed rotational sense. It will further be understood that the absolute field strengths between'the specified sets of pole faces must be carefully adjusted relative to the field of the main magnets to achieve the desired radial displacement of each beam so that collision occurs.

In operation, and with reference to Figure l inparticular, the preaccelerator systems are energized'to inject particles into the two beam orbits defined by the vacuum tanks '38 and and the main magnet current source 37 is pulsed on to confine the particles to the desired circular orbits. The particles are accelerated and bunched 'by the alternating field across the gaps 58 and 58' in resonators 51 and 51', the frequency of alternation of the field being continually increased concurrent with increase of the magnetic field through the hereinbefore described action of the saturable' reactors 62 and 62'. When the two particle beams have been brought up to the desired energy, the deflector magnet power supply 72' is pulsed resulting in the outer beam being deflected inward in straight section 19 and in the inner beam being directed outward. During the interval that the field of the deflectormagnets'69 and 71 is in'theprocess of risingto themaximum value, the amount of radial excursion of the two beams is found to be less than that '11eeded to effect beam collision. Since however, the dejfiector magnets act to return each beam to its proper orbit at the end of the straight section 19, the'presence of the. partial field in the deflectormagnets during the specified interval does not significantly disturb the cir-' culating beams. When the deflector magnet. fields have risen to the maximum value, the radial excursion of each beam is suchthatthe'two beams are each colinear with. the centerline of the straight section vacuum tank .73, 'and traveling in opposed directions, sothat the-desired interactions between component particle'sjof the two beams is achieved. Such'particles as do not undergo interactions are still returned to their proper orbit and recirculate with the possibility of undergoing interactions on subsequent turns. j I

In comparison with the target region of m'pst'conveh- "1b interactions with beams of given magnitude being thereby increased. i

Thus while the invention has been disclosed with respect to a single embodiment, it will be apparent-to those skilled in the art that numerous variations and modifications may be made within the spirit and scope of the invention and it is not intended to limit the'invention eX- cept a's defined in the following claims. I

What is claimed is: 7 1. In a charged particle accelerator, the combination comprising an annular magnet structure establishing a first closed curvilinear beam orbit and establishing a second closed curvilinear beam orbit which is coplanar and concentric with said first orbit and which is of less diameter, charged particle injector means injecting particles into said first orbit for circulation therein in afirst rotational direction and injecting particles into said sec.- ond orbitfor circulation therein in an opposite rotational direction, and at least one magnetic field producing means separate from said annular magnet structure, said field producing means being positioned on said orbits and establishing a field transecting said orbits whereby particles circulating in each of said orbits are converged and caused to collide. I

2. In a charged particle accelerator, the combination comprising an annular magnet characterized by a first field region establishing a closed curvilinear outer beam 1 orbit and further characterized by a second field'region of reverse polarity with respect to said'first region and establishing a closed curvilinear inner beam orbit which is concentric and coplanar with said first orbit and which is of lesser diameter, means injecting charged particles into. said outer orbit for rotation therein in a first angular direction and injecting charged particles into saidinner orbit for rotation therein in a reverse angular direction,

"and at least one magnetic field generating element positioned to straddle said inner and outer orbits at a se- 7 lected azimuthal portion thereof and having a deflector field transectin'g each of. said orbits which deflector field is of like polarity to said first field of said annular mag net, whereby particles in said outer orbit'a're curved inwardly and particles in said inner orbit are curved outwardly and collisionsbetween said particles may be eftional accelerators, a desirable characteristic jof the deflector magnets and associated structure within the beam clashing straight section 19"is that the region surround-' ing' the-center ot'the vacuum tank,'73,flinwhich the desiredbeam collisions occur, islargely free from ob struction ,and thus the various, detection instrument's customarily used for the analysis ofnuclear' events may -Variations in portions of the described. structure are possible and will suggest themselves to those skilled. in

V the art. In the deflector magnet systemf'at straight. sec-I tion 19, for example, asequence of only three magnetic fields may bev employed, in placeof the four herein described, the'two outer fields being of one polarityand the'middle field being of reverse polari'tyjfiWith the fthree field system the beam collision occurs only at one point rather than along an" extended linefandris thus advantageous from the standpoint of fixing .the exact; position of-the detected nuclear event but has the disadvantages.

of lessened probability of particleinteraction, partialiob- V -structionbfthe particle interaction. zone by the-{middle magnet structure, and deflection of charged secondary uice .21, the probability for effecting,the desired nuclear 375 I fected.

3. Ina charged particleaccelerator, the combination comprising a ring "magnet havingfirst and second field regions of opposite polarity defining two concentric-coplanar substantially-circular beam orbits, a first of said orbits being of greater' diameter than a second of said orbits, means injecting charged particles into said first field region for circulation in saidfirst orbit, means injectingcharged particles into said second orbit for circulationtherein in a rotational direction opposite to that of particles in said firstorbit, and aplurality of deflector magnets positioned along a portion of said orbitsteach straddling" said orbits and each establishing, a magnetic field substantially normal .to each of said orbits, the two terminal ones of said deflector magnets having a polarity similar to that ofsaid'fir'st field region and at leastone central one ofsaid magnets having. apolarity similar to that of said second field region whereby'particles in each of said orbits are converged to a common trajectory at :least' one point andare subsequently returned to said orbits. v

A charged particle accelerator substantially na scribed in clai'r n 3wher ein said defiector'magnets are :four' in number-and each of the two centralones of saidmag- ,netshave a polarity similar tothat of said second 'fild'i I region;

5. 1A clashing ibeam chargedi particle accelerator com- "prising, in combination -an annular electromagnet characterized by twp ar'inula fluxgaps for the containment forcontra rotating charge particle beams which g aps are a [concentric anda'iirsbof-iwhich is' ot greaterfdiameter thane-the second, means: for-directing chargedparticlesl 11 into each of said flux gaps for rotation therearound in opposed angular directions to establish said contrarotating beams, means for applying an alternating electrical field along a portion of each said fluxgap for accelerating said particles therein, and a magnetic deflector having at least threefield regions traversed by each of said contra-rotating charged particle beams, two spaced apart ones of said field regions having a polarity similar to that of said first flux gapof said electromagnet and an intermediate one of said field regions having a polarity similar to that of said second flux gap of said electromagnet whereby said contra-rotating beams are caused to converge at one portion of the orbits of said beams and to subsequently diverge for recirculation in said orbits.

6. A clashing beam charged particle accelerator substantially as described inclaim and wherein said two .fiux gaps of said annular electromagnet are of opposite polarity and said means for directing charged particles into each of said flux gaps injects like particles into each ,of said gaps.

7. A clashing beam charged particle accelerator comprising, in combination, an electromagnet having two concentric rings of spaced apart pole pairs for establishingtwo concentric annular flux gaps of opposed magnetic polarity which gaps define two concentric coplanar particle beam orbits, a pulsed electrical power source connected toenergize said electromagnet, means injecting charged particles into a first-of said orbitswith a clockwise rotational direction therein and injecting charged particles into a second of said orbits with a counterclockwise rotational direction therein, a first electrical oscillator applying an alternating electrical field along a portion of said first orbit said oscillator havingan operating frequency which increases as the field of said electromagnet increases, a second electrical oscillator applying alternating electrical field along a por- -tion of said second orbit which oscillator hasan operating frequency which increases as the field of said electromagnet increases, and a pulsed deflector magnet having at least one pair of spaced apart magnet poles which poles are disposed one each side of a selected portion of said .orbits whereby a field transecting said orbitstis established and particles in each of said orbits may be caused to converge. V 3

8. A clashing beam accelerator substantially as described in claim 7 wherein said deflector magnet is electrically connected with said pulsed electrical current source and is pulsed concurrently with said electromagnet. T

9. A clashing beam particle accelerator substantially as described in claim 7 and comprising the further "combination of a second pulsed electrical power supply connected to energize said deflector magnet independently of energization of said electromagnet. 3

10. Apparatus for accelerating and colliding oppositely directed charged particle beams comprising, in combination, a vacuum envelope enclosing two concentric coplanar charged particle orbits" a'first 'of 'Which orbits is of greater diametertha'n the 'second,"aiplu- .rality of magnet pole pairs distributed around each .of said orbits, one pole of each pair thereof being on each side of the associated orbit to establish aamagnetic: flux transecting said-orbit, a pulsedtcurrent source connected in energizing relationship with said magnet poles toI-pro- 'vide 'for oppositely directed magnetic fields across-said 'orbits, a charged particle injector supplying particle's-to .said first orbit for-circulation therearound, with a first ,rotational direction, ajcharged particle'injector supplying particles to said second orbit for circulatiomtliere- .around inan opposed rotational direction, a firsLyaritable frequency, oscillator applying an alternatingfield along a section of said first orbitfor;;acce lerating par {ticles circulating therein, said first oscillator-,being ,syn- 'tchronized with said pulsed, current; source to' oscillate rat-an increasing frequency said fiuxj across aaidlprbita 12 increases, asecond variable frequency oscillator applying an alternating field along a section of said second orbit, said second oscillator being synchronized with said pulsed current source to oscillate at an increasing fre- 5 quency as the flux across said orbit increases and to oscillate at a frequency exceeding that of said first oscillator, and a deflector magnet structure h aving a plurality of spaced apart pole pairs forming a plurality of magnetic flux gaps each traversed by each of said orbits, in atleast one central one of said flux gaps having a field direction similar to that associated with said second orbit and .at least one ofsaid flux gaps on each side of said central one of said flux gaps having a field direction similar to that associated with said first orbit, whereby 1 5 contrarotating particles in said two orbits are caused to converge in said deflector magnet structure and to subsequently diverge and return to said orbits. f

11. Apparatus for accelerating and colliding oppositely directed charged particle beams substantially as described in claim 10 wherein said magnet pole pairs of said deflector magnet structure areat least four in number and the two central ones thereof are separated by a substantial field free gap whereby a beam colliding region is provided which-region is substantially free from 2 5 obstruction by surrounding magnet structures thereby enabling detection instruments to be readily placed therearound. e p

a 12. A charged particle beam accelerator providing for the colliding ofoppositely directed charged particle beams comprising, in combination, a vacuum envelope enclosing two closed concentric and coplanar charged particle orbitsjwhich orbits are characterized by arcuate portions interposed with linear portions and a first of which [orbits is of-gre'ater radius than the second, an

clectromagnet formed of a plurality of pole pairsdistributed around saidarcuate portions of each of said orbits, one pole of each said pair thereof being on each side of the plane of the associated orbit to providea flux transacting said orbits at the arcuate portions there- 40 of, a source of pulsed current connected to energize said electromagnet and to provide magnetic fields of opposite polarity across said orbits, means injecting like charged particles into each of said orbits for circulation there- Iinincqntra-rotating relationship, a pair of variable frequency oscillators one associated with each of said orbits and each having an accelerating'electrode positioned adjacent theassociated orbit to provide an alternating electricalfieldtherealong, said oscillators being synchronously energized withtsaid electromagnet to provide for an increasing frequency of oscillation as, the fieldof said electromagnet, increases, and a .pulsed beam don- :yerging deflector magnet disposedralong one of said linear sections of said orbits and having four pairsof spaced .apartpoles, between which poles said orbits passfthe 5 two outer'ones of said pole pairs havingfa polarityjcoi responding to that of the principle electromagnet poles associated with said first orbit and the two central ones of said deflector magnet pole' pairs having a reverse polarity whereby'pa-r'ticles circulating in said two orbits were caused ,to converge for collision and particles not ,undergoing, collision are returned to the original orbits for recirculation therein. a, l Y t I 1 3. A deflector magnet structure for effecting the col- "lision of two oppositely directed beams of similar charged particles which beams areseparatc and substantially par- 7 allel comprising, incombination, at least four pairsot 'electromagnet poles disposed along said two beams, the twopoles forming'each pair being spaced apart with one 'rnember' thereofon each side of of the plane de- 'find by'said beams whereby each said pairof poles 'providesla fielddransectmg saidbeams, and a source' of pulsed current connected to energize each of said pole pairs and connected to establishafirst field polarity within the twozcntrabones of said pole pairs and to establish (5 :areverse rfield ;,polarity within the-rtwo out'er ones of said pole pairs whereby said beams are caused to con- References Cited in the file of thispatent UNITED STATES PATENTS Smith June 14, 1949 McMillan Jan. 6, 1953 Courant et al. Apr. 14, 1959 Ohkawa June 9, 1959 

